In a manufacturing process of a tire, various inspections are performed on a manufactured tire for quality control. As one of the inspections, a dynamic balance when the tire is rotated (hereinafter, referred to as a dynamic balance) is measured.
A tire balance measurement device which inspects the dynamic balance of a tire includes a lower rim and an upper rim which interposes a tire therebetween, a main shaft which is integrally provided with the lower rim, a rotation drive mechanism which rotationally drives the main shaft, and an eccentric amount detection sensor which detects an eccentric amount generated in the main shaft. The tire balance measurement device rotates the main shaft by the rotation drive mechanism in a state where the tire interposed between the lower rim and the upper rim is filled with air. The tire interposed between the lower rim and the upper rim integrally rotates with the main shaft by the rotation of the main shaft. The tire balance measurement device detects the eccentric amount generated in the main shaft when the tire is rotated, and thereby, measures the dynamic balance (unbalance amount) of the tire.
In the tire balance measurement device, in order to secure measurement accuracy, it is necessary to calibrate a balance of the lower rim, the upper rim, and the main shaft. PTL 1 discloses a calibration method of a tire balance measurement device using a sinker whose weight is known. In this method, in each of a case where the sinker is mounted on only the lower rim, a case where the sinker is mounted on only the upper rim, a case where the sinker is mounted on the lower rim and the upper rim, and a case where the sinker is not mounted, the lower rim, the upper rim, and the main shaft are rotated and an eccentric force of the main shaft is detected. The tire balance measurement device is calibrated from a measurement result of the eccentric force when the sinkers whose weights are known are mounted and the lower rim, the upper rim, and the main shaft are rotated.